Equity Incentive Plans, Employee Stock Purchase Plan and Stock-Based Compensation (Tables)
|
12 Months Ended |
Dec. 31, 2019 |
Summary of Option Activity |
The following table summarizes option activities under the Company’s 2004 Plan and 2018 Plan:
|
|
Outstanding
Options
|
|
|
Weighted-
Average
Exercise Price
|
|
|
Weighted-
Average
Remaining
Contract Term
(Years)
|
|
|
Aggregate
Intrinsic Value
(in thousands)
|
|
Balances at December 31, 2017
|
|
|
835,320
|
|
|
$
|
10.31
|
|
|
|
6.84
|
|
|
$
|
3,813
|
|
Granted
|
|
|
2,312,821
|
|
|
$
|
14.85
|
|
|
|
|
|
|
|
|
|
Exercised
|
|
|
(20,009
|
)
|
|
$
|
6.53
|
|
|
|
|
|
|
|
|
|
Canceled/Forfeited
|
|
|
(16,414
|
)
|
|
$
|
14.49
|
|
|
|
|
|
|
|
|
|
Balances at December 31, 2018
|
|
|
3,111,718
|
|
|
$
|
13.74
|
|
|
|
8.76
|
|
|
$
|
1,088
|
|
Granted
|
|
|
1,167,070
|
|
|
$
|
10.86
|
|
|
|
|
|
|
|
|
|
Exercised
|
|
|
(35,204
|
)
|
|
$
|
5.10
|
|
|
|
|
|
|
|
|
|
Canceled/Forfeited
|
|
|
(370,920
|
)
|
|
$
|
14.33
|
|
|
|
|
|
|
|
|
|
Balances at December 31, 2019
|
|
|
3,872,664
|
|
|
$
|
12.89
|
|
|
|
7.88
|
|
|
$
|
2,119
|
|
Exercisable at December 31, 2019
|
|
|
1,713,295
|
|
|
$
|
12.49
|
|
|
|
6.60
|
|
|
$
|
1,531
|
|
|
Summary of Status and Activity of Non-vested RSUs |
A summary of the status and activity of non-vested RSUs during the years of December 31, 2019 and 2018 is as follows:
|
|
Number of
shares
|
|
|
Weighted
Average
Grant-Date
Fair Value
|
|
Non-vested December 31,2017
|
|
|
-
|
|
|
|
-
|
|
Granted
|
|
|
312,400
|
|
|
$
|
15.20
|
|
Canceled
|
|
|
(1,160
|
)
|
|
$
|
15.20
|
|
Non-vested December 31,2018
|
|
|
311,240
|
|
|
$
|
15.20
|
|
Granted
|
|
|
154,900
|
|
|
$
|
11.45
|
|
Released
|
|
|
(114,103
|
)
|
|
$
|
15.00
|
|
Canceled
|
|
|
(16,238
|
)
|
|
$
|
12.46
|
|
Non-vested December 31,2019
|
|
|
335,799
|
|
|
$
|
13.49
|
|
|
Schedule of Fair Value of ESPP Shares Using Option Pricing Model |
For the year ended December 31, 2019, the fair value of ESPP shares was estimated using the following assumptions:
|
|
Year Ended December 31,
|
|
|
|
2019
|
|
|
2018
|
|
Expected term (in years)
|
|
0.5
|
|
|
0.5
|
|
Expected volatility
|
|
63.04%-83.17%
|
|
|
|
55.28
|
%
|
Risk-free interest rate
|
|
1.92%-2.51%
|
|
|
|
2.37
|
%
|
Expected dividend
|
|
|
-
|
|
|
|
-
|
|
|
Schedule of Stock-Based Compensation Expense Recognized |
Total stock-based compensation expense recognized was as follows:
|
|
Year Ended December 31,
|
|
|
|
2019
|
|
|
2018
|
|
|
2017
|
|
|
|
(in thousands)
|
|
|
|
|
|
Research and development
|
|
$
|
1,915
|
|
|
$
|
619
|
|
|
$
|
119
|
|
General and administrative
|
|
|
8,397
|
|
|
|
2,253
|
|
|
|
1,272
|
|
Total
|
|
$
|
10,312
|
|
|
$
|
2,872
|
|
|
$
|
1,391
|
|
|
Employee Stock Options |
|
Schedule of Employee Stock Options Valuation |
For determining stock-based compensation expense under the Plan, the fair-value-based measurement of our share-based payments were estimated as of the date of grant using the Black-Scholes option pricing model with assumptions as follows:
|
|
Year Ended December 31,
|
|
|
|
2019
|
|
|
2018
|
|
|
2017
|
|
Expected term (in years)
|
|
4.54-7.01
|
|
|
5.3-6.1
|
|
|
5.5-6.1
|
|
Expected volatility
|
|
72.72%-74.89%
|
|
|
54.57%-62.38%
|
|
|
56.52%-58.55%
|
|
Risk-free interest rate
|
|
1.42%-2.55%
|
|
|
2.67%-3.11%
|
|
|
1.89%-2.18%
|
|
Expected dividend
|
|
|
-
|
|
|
|
-
|
|
|
|
-
|
|
|